In this specification, the term "effusive material" is intended to encompass sufficient breadth to include any suitable vaporizable or effusive substance that may be desirably diffused within the internal confines of a cathode ray tube. Examples of such usage includes gettering or gas adsorbing substances, selected gases and discrete metallic deposits. Dispensing containers for such effusive materials have been positioned at various locations within the tube to achieve maximum accomplishment of the desired results.
By way of example, in certain types of color cathode ray tubes, gettering structures have been affixed to the forward portion of the electron gun assembly, and projected therefrom by wand-like support means to positions adjacent to the coated interior surface of the funnel. During subsequent tube processing, the effusive material emanating from the getter structures so positioned, is usually deposited over an expansive area of the funnel-disposed conductive coating.
In some tube constructions, two or more diverse but electrically-related coatings are disposed on discrete interior regions of the funnel portion. In such instances, the dispersal of an extensive area of gettering material thereover becomes a deleterious factor as such may effect electrical leakage between the coated areas. Diffusion directive means have been designed and incorporated with the getter containers to help control the effusion of material emanating therefrom, but adequate and consistent control is difficult to achieve, especially when the effusive container is positioned proximal to the diversely coated areas.
To minimize the above noted problem, the effusive structure, such as a gettering means, has been oriented in the forward region of the tube envelope, distal to the respective coatings, whereat it may be affixed to a screen-related member, such as the color tube shadow mask structure. It has been found that the desired effects of such advantageous placement of the exemplary gettering means, prior to the sealing of the face panel to the funnel portion of the envelope, are often minimized by the internal environmental conditions encountered during the panel-to-funnel sealing procedure. The internal ambient atmosphere in conjunction with the heat required for sealing produces a temperature-related environment which adversely affects the subsequent quality of the effusive material.